From the pages of Time magazine to the rules of the new “Fallout” game, polyamory seems suddenly to be everywhere — and very present in the public consciousness.

When the Supreme Court extended marriage equality to same-sex couples in all 50 states, Fox News anchor Martha MacCallum mused that same-sex marriage might soon lead to marriages of three people or more. Polyamory.

Also known as “consensual non-monogamy,” polyamory comes in a number of flavors, including swinging, polyfidelity, open relationships, and relationship anarchy. It is sometimes lumped in with polygamy — a tradition of husbands taking on multiple wives, practiced in many parts of the Muslim world and by some Mormon offshoots — especially by outsiders with only a glancing familiarity with the subject. But practitioners of both systems tend to see themselves as quite distinct, even if the general public does not.

Now the recent marriage of three women in Brazil has some activists wondering, “Is polyamory next?”

Exact numbers for individuals practicing non-monogamy can be maddeningly hard to come by. But most researchers estimate that a full 4–5 percent of Americans participate in some form of ethical non-monogamy. In her Psychology Today blog post on May 9, 2014, Elisabeth Sheff relates the findings of independent Australian academic Kelly Cookson:

“It appears that sexually non-monogamous couples in the United States number in the millions. Estimates based on actually trying sexual non-monogamy are around 1.2 to 2.4 million. An estimate based solely on the agreement to allow satellite lovers is around 9.8 million. These millions include poly couples, swinging couples, gay male couples, and other sexually non-monogamous couples.”

Who they are may surprise you.

A 2012 survey of 4,062 poly-identified individuals ages 16 to 92 conducted by Loving More — a polyamory support and advocacy organization — found a number of interesting data points.

There are more women than men: Essentially half of the respondents (49.5 percent) identified as female, while only 35.4 percent identified as male. The remaining 15.1 percent either declined to choose between male and female or wrote in “third” genders such as two-spirit and genderqueer.

The survey didn’t ask respondents to state their sexual orientation, but about half of the female respondents and about a fifth of the male respondents were actively bisexual, having had sex with both men and women within the preceding 12 months. When compared with the general population — by way of the biennial General Social Survey (GSS) — the self-identified poly population was slightly, but significantly, happier than the general population, and better educated.

At least 25.8 percent of those taking the survey, however, had personally experienced discrimination because of their lifestyle.But the data from a March 2015 Gallup poll clearly shows a growing tolerance for relationships and situations outside the bounds of traditional monogamous marriage.

Compared with similar data collected by Gallup in 2001 and 2002, there has been a 15 percent growth in those who view sex between an unmarried man and woman as morally acceptable, and an increase of 16 percent in the acceptability of having a baby out of wedlock. Acceptance of divorce is up 12 percent. And tolerance for “polygamy” is up to 16 percent, which may not seem like much, but it’s more than twice the 7 percent who found it to be morally acceptable in 2001. Support for each of these indicators is at an all-time high.

In the court of public opinion, however, not all consensual non-monogamous relationships are created equal. A paper published online in September 2013 in the journal Psychology & Sexuality found that those in polyamorous relationships are seen in a more positive light than either swingers or those in open relationships. In 13 different areas there were significant perceived differences between the three consensual non-monogamy strategies under scrutiny. Those in polyamorous relationships were regarded as more moral, more motivated by duty (rather than pleasure), and more family-oriented than swingers and those in open relationships.

With low levels of acceptance around polygamy and the general population’s lack of understanding of or knowledge about polyamory, it might be tempting to dismiss the possibility that three people (or more) could be legally wed in the United States, but in 2001 support for same-sex marriage in this country was around 40 percent. Now it’s 60 percent.

Given the trends, popular acceptance of — and even legal recognition for — marriages between more than two people is likely not a question of “if” but rather “when.” And given how quickly public opinion has shifted on same-sex marriage, “when” could be sooner than anyone expects.